[PATCH v2 0/9] evm: Support signatures on stacked filesystem

Stefan Berger
2024-02-05T18:25:34Z

EVM signature verification on stacked filesystem has recently been
completely disabled by declaring some filesystems as unsupported
(only overlayfs). This series now enables copy-up of "portable
and immutable" signatures on those filesystems and enables the
enforcement of "portable and immultable" as well as the "original"
signatures on previously unsupported filesystem when evm is enabled
with EVM_INIT_X509. HMAC verification and generation remains disabled.

"Portable and immutable" signatures can be copied up since they are
not created over file-specific metadata, such as UUID or generation.
Instead, they are only covering file metadata such as mode bits, uid, and
gid, that will all be preserved during a copy-up of the file metadata.

Regards,
Stefan

v2:
- Added patch to rename backing_inode to real_inode (1/9)
- Added patches renaming flag and function due to RSA enablement (7,8/9)
- Added patch to record i_version of real_inode for change detection (9/9)
- Use Amir's function to get inode holding metadata now (4,5/9)

Stefan Berger (9):
ima: Rename backing_inode to real_inode
security: allow finer granularity in permitting copy-up of security
xattrs
evm: Implement per signature type decision in
security_inode_copy_up_xattr
ima: Reset EVM status upon detecting changes to the real file
evm: Use the inode holding the metadata to calculate metadata hash
evm: Enforce signatures on unsupported filesystem for EVM_INIT_X509
fs: Rename SB_I_EVM_UNSUPPORTED to SB_I_EVM_HMAC_UNSUPPORTED
evm: Rename is_unsupported_fs to is_unsupported_hmac_fs
ima: Record i_version of real_inode for change detection

fs/overlayfs/copy_up.c | 2 +-
fs/overlayfs/super.c | 2 +-
include/linux/evm.h | 13 +++++-
include/linux/fs.h | 2 +-
include/linux/lsm_hook_defs.h | 3 +-
include/linux/security.h | 4 +-
security/integrity/evm/evm_crypto.c | 2 +-
security/integrity/evm/evm_main.c | 69 ++++++++++++++++++++++-------
security/integrity/ima/ima_api.c | 28 ++++++------
security/integrity/ima/ima_main.c | 23 ++++++----
security/security.c | 7 +--
security/selinux/hooks.c | 2 +-
security/smack/smack_lsm.c | 2 +-
13 files changed, 107 insertions(+), 52 deletions(-)

--
2.43.0